This invention relates to a fused oil filled capacitor and more particularly to such a capacitor wherein the fuse is an exothermically alloyable strand.
Oil filled capacitors are typically employed in a.c. power circuits and when the capacitor fails short, the dielectric oil is heated and expands leading to rupture of the capacitor housing and a sometimes violent spraying of hot oil over adjacent equipment and circuits. Up until recently one of the most preferred dielectric oils are of the class known as polychlorinated byphenols (PCB's), which oils are relatively resistant to combustion. PCB's have been found to cause serious long term effects on the environment and capacitor manufacturers have begun to use non-halogenated oils that do not endanger the environment but that are unfortunately more flamable. It has thus become even more urgent to provide in oil filled capacitors reliable means for preventing the inadvertent introduction of the non-halogenated oils in areas where they may be ignited.
It is known to employ a meltable metal fuse in an oil filled capacitor that will open the connection between at least one of the capacitor terminals and one of the capacitor electrodes when the capacitor section develops a low impedance short. Such fuses melt and open in response to overtemperature of adjacent parts or in response to abnormally high fault currents causing self heating of the fuse.
It is also known to provide in an oil capacitor a circuit interruptor mechanism that senses the degree of distortion in the housing of a faulty capacitor and interrupt the circuit when an unsafe degree of distortion is reached.
However, when the circuit is interrupted by either of the above noted means, the circuit opening or gap is typically very small and arcing ensues across the gap. Such arcing is capable of further heating the faulty capacitor and rupturing the housing.
It is therefore an object of the present invention to provide in an oil filled capacitor an arc suppresion means in combination with a standard circuit interruption protection means.